Include rich diff in tree output

Author: mpkorstanje

junit-jupiter-api/src/main/java/org/junit/jupiter/api/AssertionFailureBuilder.java

@@ -192,9 +192,10 @@ public void buildAndThrow() throws AssertionFailedError {
 	 */
 	public AssertionFailedError build() {
 		String reason = nullSafeGet(this.reason);
+		String message = nullSafeGet(this.message);
 		var assertionFailedError = new AssertionFailedError( //
-			formatExceptionMessage(reason), //
-			formatReason(reason), //
+			formatExceptionMessage(reason, message), //
+			formatReason(reason, message), //
 			expected, //
 			actual, //
 			cause //
@@ -203,18 +204,21 @@ public AssertionFailedError build() {
 		return assertionFailedError;
 	}
 
-	private @Nullable String formatReason(@Nullable String reason) {
+	private @Nullable String formatReason(@Nullable String reason, @Nullable String message) {
 		if (mismatch) {
-			return (reason == null ? "" : reason + ", ") + "expected did not match actual";
+			// TODO: The suffix is implicit due to mismatch, but how to make explicit?
+			reason = (reason == null ? "" : reason + ", ") + "expected did not match actual";
+		}
+		if (reason != null) {
+			message = buildPrefix(message) + reason;
 		}
-		return reason;
+		return message;
 	}
 
-	private @Nullable String formatExceptionMessage(@Nullable String reason) {
+	private @Nullable String formatExceptionMessage(@Nullable String reason, @Nullable String message) {
 		if (mismatch && includeValuesInMessage) {
 			reason = (reason == null ? "" : reason + ", ") + formatValues(expected, actual);
 		}
-		String message = nullSafeGet(this.message);
 		if (reason != null) {
 			message = buildPrefix(message) + reason;
 		}

junit-platform-console/junit-platform-console.gradle.kts

@@ -18,7 +18,7 @@ dependencies {
 	compileOnlyApi(libs.jspecify)
 
 	shadowed(libs.picocli)
-	// TODO: Sort out
+	// TODO: Sort out relocation, licence, ect
 	shadowed(libs.javadiffutils)
 
 	osgiVerification(projects.junitJupiterEngine)
@@ -31,7 +31,8 @@ tasks {
 		options.compilerArgs.addAll(listOf(
 			"-Xlint:-module", // due to qualified exports
 			"--add-modules", "info.picocli",
-			"--add-reads", "${javaModuleName}=info.picocli"
+			"--add-reads", "${javaModuleName}=info.picocli",
+			"-Xlint:-requires-automatic", // Java diff utils
 		))
 		options.errorprone.nullaway {
 			excludedFieldAnnotations.addAll(

junit-platform-console/src/main/java/org/junit/platform/console/output/RichDiffFormatter.java

@@ -10,20 +10,16 @@
 
 package org.junit.platform.console.output;
 
+import java.util.function.Function;
+
 import com.github.difflib.text.DiffRowGenerator;
 
-import org.junit.platform.commons.util.ExceptionUtils;
 import org.opentest4j.AssertionFailedError;
 
 final class RichDiffFormatter {
 	public String format(AssertionFailedError assertionFailed) {
-		if (!(assertionFailed.isActualDefined() && assertionFailed.isExpectedDefined())) {
-			return ExceptionUtils.readStackTrace(assertionFailed);
-		}
-
 		StringBuilder builder = new StringBuilder();
 
-		builder.append(assertionFailed.getClass().getSimpleName());
 		if (assertionFailed.isReasonDefined()) {
 			builder.append(": ");
 			builder.append(assertionFailed.getReason());
@@ -33,12 +29,43 @@ public String format(AssertionFailedError assertionFailed) {
 		builder.append("+ actual - expected");
 		builder.append(System.lineSeparator());
 
-		var generator = DiffRowGenerator.create().mergeOriginalRevised(true).build();
+		var generator = DiffRowGenerator.create() //
+				.lineNormalizer(Function.identity()) // Don't normalize lines
+				.showInlineDiffs(false) //
+				.build();
 
-		// TODO: But how to render the stacktrace?
+		var diffRows = generator.generateDiffRows( //
+			assertionFailed.getExpected().getStringRepresentation().lines().toList(), //
+			assertionFailed.getActual().getStringRepresentation().lines().toList() //
+		);
 
-		builder.append(generator.generateDiffRows(assertionFailed.getExpected().toString().lines().toList(),
-			assertionFailed.getActual().toString().lines().toList()));
+		diffRows.forEach(diffRow -> {
+			switch (diffRow.getTag()) {
+				case INSERT -> {
+					builder.append("+ ");
+					builder.append(diffRow.getNewLine());
+					builder.append(System.lineSeparator());
+				}
+				case DELETE -> {
+					builder.append("- ");
+					builder.append(diffRow.getOldLine());
+					builder.append(System.lineSeparator());
+				}
+				case CHANGE -> {
+					builder.append("+ ");
+					builder.append(diffRow.getOldLine());
+					builder.append(System.lineSeparator());
+					builder.append("- ");
+					builder.append(diffRow.getNewLine());
+					builder.append(System.lineSeparator());
+				}
+				case EQUAL -> {
+					builder.append("  ");
+					builder.append(diffRow.getNewLine());
+					builder.append(System.lineSeparator());
+				}
+			}
+		});
 
 		return builder.toString();
 	}

junit-platform-console/src/main/java/org/junit/platform/console/output/TreePrinter.java

@@ -22,6 +22,7 @@
 import org.junit.platform.engine.TestExecutionResult.Status;
 import org.junit.platform.engine.reporting.FileEntry;
 import org.junit.platform.engine.reporting.ReportEntry;
+import org.opentest4j.AssertionFailedError;
 
 /**
  * @since 1.0
@@ -123,11 +124,19 @@ private void printThrowable(String indent, TestExecutionResult result) {
 			return;
 		}
 		Throwable throwable = result.getThrowable().get();
+		String message = formatThrowable(throwable);
+		printMessage(Style.FAILED, indent, message);
+	}
+
+	private static String formatThrowable(Throwable throwable) {
+		if (throwable instanceof AssertionFailedError assertionFailedError) {
+			return new RichDiffFormatter().format(assertionFailedError);
+		}
 		String message = throwable.getMessage();
 		if (StringUtils.isBlank(message)) {
 			message = throwable.toString();
 		}
-		printMessage(Style.FAILED, indent, message);
+		return message;
 	}
 
 	private void printReportEntry(String indent, ReportEntry reportEntry) {

platform-tests/src/test/java/org/junit/platform/console/output/RichDiffFormatterTests.java

@@ -19,30 +19,74 @@
 class RichDiffFormatterTests {
 
 	@Test
-	void test() {
-		var expected = """
+	void lineAdded() {
+		assertRichDiffEquals("""
+				{
+				  "speaker": "world"
+				}
+				""", """
 				{
 				  "speaker": "world"
 				  "message": "hello"
 				}
-				""";
-		var actuall = """
+				""", """
+				expected did not match actual
+				+ actual - expected
+				  {
+				    "speaker": "world"
+				+   "message": "hello"
+				  }
+				""");
+	}
+
+	@Test
+	void lineRemoved() {
+		assertRichDiffEquals("""
 				{
-				  "speaker": "you"
+				  "speaker": "world"
 				  "message": "hello"
 				}
-				""";
+				""", """
+				{
+				  "speaker": "world"
+				}
+				""", """
+				expected did not match actual
+				+ actual - expected
+				  {
+				    "speaker": "world"
+				-   "message": "hello"
+				  }
+				""");
+	}
 
-		var assertionFailed = assertThrows(AssertionFailedError.class, () -> assertEquals(expected, actuall));
+	@Test
+	void lineChanged() {
+		assertRichDiffEquals("""
+				{
+				  "speaker": "world"
+				  "message": "hello"
+				}
+				""", """
+				{
+				  "speaker": "you"
+				  "message": "hello"
+				}
+				""", """
+				expected did not match actual
+				+ actual - expected
+				  {
+				+   "speaker": "world"
+				-   "speaker": "you"
+				    "message": "hello"
+				  }
+				""");
+	}
 
+	private static void assertRichDiffEquals(String expected, String actual, String expectedDiff) {
 		var formatter = new RichDiffFormatter();
-
-		String message = formatter.format(assertionFailed);
-
-		assertEquals("""
-
-				""", message);
-
+		var assertionFailed = assertThrows(AssertionFailedError.class, () -> assertEquals(expected, actual));
+		assertEquals(expectedDiff, formatter.format(assertionFailed));
 	}
 
 }